Research question

What is the contribution of diet to toenail metals concentrations in three-year-old participants of the New Hampshire Birth Cohort Study?




Plan

  1. Explore relationships between foods and toenail metals using Spearman Correlation Coefficients, make correlogram

  2. Estimate overall contribution of diet to variation in toenail metals using multiple adjusted R2

  3. Estimate effect of [amount] increase in specific food per day on toenail metal concentration, adjusting for covariates. Use multivariable linear regression
    Ln transform all biomarkers to improve model fit, normalize residuals

    Exponentiate coefficients to represent percent change in biomarker concentration based on increase of 10 grams per day(?) for each food

  4. Principal component analysis to group food and predict different toenail metals?




Table 1. Summary Statistics

Characteristic N N = 5321
Male 532 274 (52%)
Maternal smoking status 511
0 459 (90%)
1 22 (4.3%)
2 30 (5.9%)
Maternal age (years) 532 31.1 (28.3, 34.4)
Child age at questionnaire (days) 532 1,086 (1,077, 1,094)
Season of toenail collection 531
1 123 (23%)
2 148 (28%)
3 146 (27%)
4 114 (21%)
Toenail sample weight (ng) 531 0.010 (0.006, 0.016)
Al_T 532 55.43 (27.39, 109.71)
As_T 532 0.32 (0.17, 0.55)
Cd_T 532 0.04 (0.02, 0.08)
Co_T 492 0.05 (0.03, 0.11)
Cr_T 532 0.53 (0.29, 0.99)
Cu_T 532 5.94 (4.13, 8.66)
Fe_T 532 87.10 (46.35, 190.10)
Hg_T 532 0.02 (0.01, 0.05)
Mn_T 532 1.44 (0.56, 3.26)
Mo_T 532 0.02 (0.02, 0.04)
Ni_T 532 14.07 (2.95, 57.59)
Pb_T 532 0.89 (0.45, 1.82)
Sb_T 532 0.07 (0.05, 0.12)
Se_T 532 0.92 (0.84, 1.01)
Sn_T 532 0.40 (0.23, 0.73)
U_T 236 0.03 (0.01, 0.07)
V_T 532 0.09 (0.04, 0.18)
Al_W 523 10.00 (10.00, 10.00)
As_W 523 0.04 (0.02, 0.04)
Cd_W 523 0.02 (0.01, 0.03)
Co_W 523 0.01 (0.01, 0.01)
Cr_W 515 0.60 (0.10, 0.60)
Cu_W 523 0.30 (0.03, 0.30)
Fe_W 523 10.00 (10.00, 10.00)
Hg_W 316 0.01 (0.01, 0.03)
Mn_W 523 0.10 (0.10, 0.10)
Mo_W 520 0.04 (0.04, 0.04)
Ni_W 523 0.30 (0.03, 0.30)
Pb_W 500 0.01 (0.01, 0.01)
Sb_W 523 0.01 (0.01, 0.03)
Se_W 515 0.08 (0.04, 0.08)
Sn_W 506 0.03 (0.03, 0.05)
U_W 509 0.01 (0.01, 0.01)
V_W 523 0.100 (0.100, 0.100)

1 Statistics presented: n (%); Median (IQR)

Questions about Table 1:

Notes on univariate statistics

2. Frequency dietary data statistics






Correlation plots

Some moderate correlations between toenail metals and dietary variables. You can use zoom, and then pan (cross arrows symbol) for a closer look. Nice to know, but I’m thinking it might be cleaner to leave it out of manuscript and focus on regression models.






3. Estimate overall contribution of diet to variation in toenail metals using multiple adjusted R2

Table 2. Amount of variation in 3-year-olds’ toenail metals explained by diet*

Toenail metal Adj. r-sq base model Adj. r-sq base + diet model Percent of variation explained by diet
Aluminum 0.25 0.33 0.08
Arsenic 0.07 0.16 0.09
Cadmium 0.04 0.19 0.15
Chromium 0.12 0.25 0.13
Copper 0.03 0.16 0.13
Iron 0.25 0.33 0.07
Mercury 0.05 0.27 0.22
Manganese 0.15 0.23 0.08
Molybdenum 0.09 0.20 0.11
Nickel 0.02 0.15 0.13
Lead 0.06 0.22 0.16
Antimony 0.03 0.17 0.14
Selenium 0.03 0.15 0.12
Tin 0.03 0.14 0.13
Zinc 0.01 0.14 0.13
Vanadium 0.18 0.28 0.10

*models adjusted for child sex, child age, season of toenail collection, toenail sample weight, smoking in the home, home tap water respective metal concentration





4. Regression Models for estimating the effect of 10 g increase in specific food per day on toenail metal concentration, adjusting for covariates.

Values from figure

Metal Food Estimated percent change 95%CI
Al Cold cereal 14.92 1.14 28.89
Al Hot dogs 14.24 -3.78 32.60
Al Popsicles 6.25 0.83 11.69
As Bacon/sausage 24.00 -3.89 52.68
As Cold cereal 13.83 0.10 27.75
As Crackers 13.73 -16.79 45.20
Cd Tomatoes 32.98 6.50 60.15
Cd Cold cereal 20.59 3.39 38.09
Cd Beef 19.64 -9.09 49.21
Hg Fried fish 62.96 9.71 119.01
Hg Salty snacks 31.24 -10.93 75.20
Hg Pork 28.57 -18.94 78.38
Ni Burgers 60.36 -11.94 137.94
Ni Pretzels 52.47 -21.69 132.26
Ni Rolls/muffins 45.80 9.41 83.51
Pb Tomatoes 22.60 -2.47 48.30
Pb Peanut butter 23.95 -2.34 50.94
Pb Pork 22.66 -10.79 57.24
Sb Green salad 13.93 -14.67 43.36
Sb Tortillas 19.08 -14.31 53.60
Sb Bacon/sausage 16.32 -7.85 41.08
Sn Bacon/sausage 17.64 -14.44 50.76
Sn Raisin/dried fruit 13.84 -16.60 45.22
Sn Beef 13.67 -11.72 39.70
Cr Bacon/sausage 21.60 -4.60 48.40
Cr Pancakes/waffles 11.00 -0.70 22.90
Cr Broccoli 8.50 -2.10 19.30
Cu Cheese 8.90 -0.33 18.23
Cu Green beans 10.70 1.20 20.10
Cu Tomatoes 9.80 -3.00 22.70
Fe Cold cereal 13.40 0.30 26.60
Fe Hot dogs 20.10 2.90 37.70
Fe Popsicles 5.90 0.70 11.00
Mn Cold cereal 18.10 0.30 36.30
Mn Green beans 20.10 -0.10 40.80
Mn Hot dogs 20.00 -3.50 44.00
Mo Burgers 27.33 0.40 54.90
Mo Pork 14.30 -8.00 37.10
Mo Bacon/sausage 12.20 -10.80 35.80
Se Jelly/honey/sugar 8.50 1.00 16.00
Se Nuts/seeds 4.30 -1.20 9.80
Se Cold cereal 2.10 0.40 4.60
Zn Salty snacks 6.20 -1.80 14.30
Zn Nuts/seeds 5.70 -4.90 16.40
Zn Broccoli 3.90 0.10 7.80